unsigned char  L_1 = 9;  
unsigned char  L_2 = 6;  
unsigned char  R_1 = 5;  
unsigned char  R_2 = 3;  

void L_Stop(){  
  digitalWrite(L_1, LOW);  
  digitalWrite(L_2, LOW);  
}  
void L_Fwd(){  
  digitalWrite(L_1, LOW);  
  digitalWrite(L_2, HIGH);  
}  
void L_Rvs(){  
  digitalWrite(L_1, HIGH);  
  digitalWrite(L_2, LOW);  
}  
void R_Stop(){  
  digitalWrite(R_1, LOW);  
  digitalWrite(R_2, LOW);  
}  
void R_Fwd(){  
  digitalWrite(R_1, HIGH);  
  digitalWrite(R_2, LOW);  
}  
void R_Rvs(){  
  digitalWrite(R_1, LOW);  
  digitalWrite(R_2, HIGH);  
}  

void setup(){  
  pinMode(L_1, OUTPUT);  
  pinMode(L_2, OUTPUT);  
  pinMode(R_1, OUTPUT);  
  pinMode(R_2, OUTPUT);  
}  

void loop(){  
  
  while (analogRead(0)>460) {
  L_Stop();
  R_Rvs();
  };
  L_Fwd(); 
  R_Fwd();
} 


